Abstract : L-Leucine and several amino acids proved to be effective germination inducers of microspores of Trichophyton mentagrophytes. During germination phase darkening and swelling occurred concomitantly with the alterations of several spore properties inherent to dormancy. Such changes included the loss of resistance to heat and stain, the reduction of dry weight and specific gravity, and the development of active glucose utilization. The germination induced by L-leucine was significantly stimulated by a pre-treatment of the spores with sublethal doses of heat. D-leucine proved to be almost equally effective germinant as its L-form. Other factors that affected the L-leucine induced germination of the microspores included the concentration of leucine, the inoculum size of the spores, temperature and pH. The anaerobic condition and the presence or absence of carbon dioxide had no significant effects on the germination. (Author)